(a) Field of the Invention
The present invention relates to a method for forming a titanium silicide during a process for fabricating a semiconductor device.
(b) Description of the Related Art
Silicide is widely used in manufacturing integrated circuit or semiconductor devices because of its low sheet resistance. Generally, in the case of titanium silicide, the silicide is formed by first depositing a titanium thin film using a sputtering process on a silicon wafer where source/drain regions and gate electrodes are formed. The silicon wafer is then heat-treated within an electric furnace or through RTP (rapid thermal processing) to cause the deposited titanium to react with the silicon wafer to form titanium silicide. The sheet resistance of the titanium silicide depends on the titanium thin film depositing conditions rather than the silicide forming heat-treating conditions.
The titanium thin film is usually deposited using the collimate (high power) sputtering method. In this method, metal atoms sputtered from a metal target pass through and are accelerated by a mesh disposed between the metal target and the silicon wafer. This causes the sputtered metal atoms to gain very high kinetic energy which can provide certain process advantages. However, use of the collimate sputtering method causes the metal atoms to be deposited onto the silicon wafer in a vertical direction with respect to the wafer surface. The deposition of the metal atoms in the vertical direction, in turn, causes the deposited titanium thin film to lack uniform film thickness. As a result, the resulting silicide thickness and sheet resistance have poor uniformity.